Process of producing low-boiling hydrocarbons



P, HUBBARD.

PROCESS OF PRODUCING LOW BOILING HYDROCARBONS.

APPLICATION FILED AUG. Iv I914.

1,326,056. Patented Dec. 23,1919.

s arnr Wren,"

PREVOST HUBBARD, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO THE IROLINE COMPANY OF AMERICA, OF CORPORATION OF DELAWARE.

WASHINGTON, DISTRICT OF COLUMBIA PROCESS OF PRODUCING LOW-BOILING HYDROCARBONSQ To all whom it may concern Be it known that I, PREvosr HUBBARD, a citizen of the United States, residing at lVashington, in the District of Columbia, have invented certain new and useful Improvements in Processes of Producing Low- Boiling Hydr0carbons, of which the following is a specification.

This invention relates to the treatment of liquid or fusible hydrocarbons for the purpose of producing hydrocarbons of lower boiling-point. vention, a commercial liquid or fusible hydrocarbon, usually or always comprising a mixture of various hydrocarbon bodies, is strongly heated in .a confined space under high pressure, under such conditions that hydrocarbon vapors and liquid co-eXist during the treatment. Under these conditions, the temperature and pressure being suitably adjusted, there are formed material proportions of lower-boiling hydrocarbons which are capable of replacing gasolene as a fuel for internal combustion engines, and are otherwise utilizable.

Suitable illustrative conditions in accordance with the invention, as applied to hydrocarbons of the fuel-oil type, involve a temperature, measured in the liquid phase, of 420 to 480 C., under a pressure of 300 to 500 pounds per square inch, although higher pressures may be advantageous when practicable. At the higher pressure ranges, somewhat lower temperatures may be employed, indicating that pressure andtemperature are to some degree at least correlative factors. For the best results, the temperature should not reach the coking-point of' the particular hydrocarbon body employed. It is considered satisfactory in practice to maintain the oil at or near the maximum temperature fora period of five to twenty minutes, although the invention is not limited to such time.

During and immediately after the heating of the hydrocarbon under pressure (hereinafter for convenience referred to as the processing of the hydrocarbon) there coexist in the processing vessel, a l lq111d phase and a vapor phase, together, with a small proportion of fixed gases, which last term is used to include light hydrocarbons, which are not condensable' at ordinary temperatures under atmospheric pressure. The pro Specification of Letters Patent.

In the practice of the in- Patented Dec. 23,1919.

Application filed August 1, 1914. Serial No. 854,545,

portion of the fixed gas does not ordinarily exceed three per cent: by weight of the original oil. Thelighter, easily-condensable hydrocarbons which have. been formed during the processing are dissolved in the residual liquid to the extent of their solubility therein under the existing temperature and pressure conditions. Under these conditions a portion of the fixed gases anddifficultly condensable hydrocarbons are also dissolved in the liquid phase.

It is found that the ratio between the volumes of the liquid and vapor phases exerts a profound influence upon the result of the processing, Ordinarily, this ratio is not directly determinable during the processing, but 1t is controlled by the quantity of hydrocarbon introduced into the processing vessel 'relative' to the total capacity of this vessel. Satisfactory results are obtamed, in the case of a typical fuel-oil, when the quantity introduced, measured at normal temperatures, is from one-eighth to onehalf of the total capacity. Within these limits and under generally similar conditions of temperature, pressure and time of heating, the percentage yield of low-boiling hydrocarbons (say those averaging 62 Baum) tends to rise as this ratio decreases, that is, as the proportion of liquid introduced relative to the total capacity of the vessel is' less. On the other hand, the total yield of such low-boiling:hydrocarbons tends to increase as this ratio'increases; so that the precise'ratio to be selected depends not only upon the hydrocarbon to be treated, but also upon commercial factors. riation of the yield according to the ratio chosen is illustrated in the specific examples herein given.

Following the processing, the charge is cooled, preferably to substantially normal temperature, or at least to or below the distillation point, at the pressure chosen for distillation, of the lighter liquefiable con- This vz I from the processing vessel into the same or other cooling system, the vapors being condensed, and the fixed gases released when their temperature has been sufiiciently reduced. When so desired, the residual liquid, containing the dissolved lighter hydrocarbons, may be collected separately from the condensed vapors; or the two may be permitted to mix and subsequently fractionated by known methods. When the residual liquid is separately collected, it is found, under the specific conditions above described, to carry about six per cent. by weight of volatile hydrocarbons condensable to a liquid of 62 Baum.

For a fuller explanation of the invention, reference is made to the accompanying drawing illustrating diagrammatically one form of apparatus for carrying the process into effect.

In said drawing, 1 indicates the processing vessel, which may consist of a strong steel shell capable of hermetic closure and adapted to withstand pressures of the order above mentioned or higher. This is preferably mounted with a very slight downward inclination to the outlet end. Heat may be applied to this vessel by means of a gas or oil burner indicated at 2. The oil to be processed is introduced by means of a pump (not shown) through the valved inlet pipe 3, and at the close of the processing treatment the contents of the vessel 1 are discharged through an outlet pipe 4 provided with a valve 5, this outlet pipe leading directly to the cooling system. In the particular apparatus illustrated, this cooling system comprises a coil 6 immersed in a cooling tank 7, and in connection therewith a reservoir or separating drum 8 in a cooling tank 9. Pressure gages 10 and 11 are connected respectively with the processing vessel and the reservoir 8. This reservoir is also fitted with a valved gas-outlet pipe or vent 12, and with a draw-off 13 for the liquid and liquefied processed material. 14, 14 indicate tubes extending into the vessel 1 in such manner as to dip below the liquid-level indicated by the dotted line 15; thesetubes are closed at the bottom and open upwardly, and are intended for the reception of thermometers, pyrometer wires, or any suitable temperature-indicating means. The capacity of the separating drum 8 should be ample to receive the entire liquid and readily liquefiable contents of the processing vessel.

An illustrative example of the process is as follows, it being understood that the in vention is not restricted to the specific conditions recited The-material treated was a typical commercial fuel-oil from which the tops had been removed. Its specific gravity was .884 at 3 C., and it yielded only 0.75 per cent. of distlllate to 175 C. This oil was pumped distillate.

contents discharged into the cooling system,

and the pressures were permitted to equalize in the processing vessel and the cooling system, the outlets 12 and 13 being closed. After about two minutes, a pressure of 190 pounds was indicated at the pressure gages 10 and 11. At this moment the gas-vent 12 was slightly opened, and after about two minutes more, both gages indicated zero pressure. The valve 5 was then closed and the introduction of oil and the heating were recommenced in the processing vessel. The processed material, comprising the solution drawn from the processing vessel and the condensed vapors from this vessel had a specific gravity of .868 at 29 (1, and yielded 15.5 per cent. by volume of 62 Baum dis tillate.

The second processing operation was car-.

same grade of oil, but with a ratio (volume of oil introduced tototal capacity of vessel) of 26.8 to 100, gave a processed material having a specific gravity of .872 at 29 C., which yielded 11.5 per cent. by volume of 62 Baum distillate.

When the residues from the distillation are reprocessed under substantially the same conditions, they yield a further, but usually somewhat less, proportion of 62 Baum The reprocessing may be repeated several times with gradually diminishing yield.

The operation above described is essentially intermittent, in the sense that the processing vessel is evacuated to zero pressure at the existing temperature after each operation. This offers the material advantage that in successive repetitions of the process, with new charges of oil, the pressures developed are due almost in their entirety to volatile products derived from the new charge, the desired decomposition of which therefore proceeds further.

It is practicable, however, to operate the process either in a semi-continuous or continuous manner.

In the first instance, oil is introduced and liquid residue withdrawn at -is to say, the

processing vessel,

times from subsequent re-processings,

brief intervalsyat such rate as to maintain a substantially constant liquid-level in the processing vessel, a small allowance being made, if desired, for the formation of fixed gases. In the second instance, oil is continuously introduced and liquid residue withdrawn, the liquid-level being substantially maintained. In either instance, the desired low-boiling'hydrocarbons are withdrawn exclusively in solution in the liquid residues, this solution being first cooled and then distilled as above described. In proceeding either semi-continuously or continuously, it is desirable to maintain as high a degree of pressure in the processing vessel as .i's'practicable, in order to increase the proportion of low-boiling hydrocarbons dissolved in the liquid. The rate of inflow and outflow may be adjusted to allow the material to remain under high temperature and pressure for five to twenty minutes, as in the intermittent operation.

The intermittent operation first described may be combined with either the continuous or the semi-continuous operation that process may be carried out semi-continuously or continuously for any desired period, at the close of which the solution is completely withdrawn from the followed by the condensation of the easily liquefied vapors and the release of the fixed gases, thereby evacuating the apparatus to zero pressure, preparatory to a new operation.

The distillate obtained according to the present process is white or very slightly c01- ored, and is notably free from ofi'ensive odors, and especially from the characteristic pungent odor of so-called cracked distillates. The distillates are practically without bloom.

The invention is not limited to the treatment of the particular oil described by way of example, as the process is applicable to many products of similar or analogous na ture, including various petroleum distillates, residues and products, crude petroleum, and malthas, asphalts, tars and products of analogous character derived there from. Such materials are herein collectively referred to as liquid or fusible hydrocarbons.

As applied to the grades of oil commercially known as fuel-oils, the process possesses the great advantage that the residues from the first processing at least, and someare yet liquid and mobile, and are free from separated carbon which might clog the burners or otherwise interfere with their eflicient operation, in marked contrast to the heavy semi-liquid or even solid products resulting from the so-called cracking processes. For example, in the specific cases above mentloned, the original oil had a specific gravity of .88t at 30 (land the mixed residues after removing the 62 Baum distillate, had a specific gravity of .896 at 29 0., the slightly higher gravity of the residue, combined with its mobility, rendering it as well or even better adapted for use as fuel than the original fuel-oil. With each re-processing of the same material, the residue becomes heavier, less mobile, and ultimately may separate carbon. It follows from the above that the present process, applied to the treatment of a fuel-oil, renders it possible-to prepare therefrom a very considerable proportion of light hydrocarbons suitable for use in internal combustion engines, without at all impairing the value of the residue, per unit of weight or volume, for fuel-oil purposes.

The present process is distinguished from so-called pressure-distillation processes, in which the Vapors are withdrawn and condensed at substantially the same rate as they are produced, by the fact that according to the present process, the lighter hydrocarbons resulting from the heating under pressure are wholly or partly withdrawn from the processing; vessel in solution in the residual hydrocar then treated for the recovery of the hydrocarbons suitable for use in internal combus tion engines. By proceeding in this way, the tendency'to the formation of free carbon or coke and fixed gases is greatly lessened, the light distillates eventually obtained are quite free from disagreeable odors, and the resi dues are directly available either essing or for use as fuel-oils or oses:

I claim v 1. Process of treating liquid or fusible hydrocarbons to produce therefrom hydrocarbons of lower boiling point, comprising for re-procfor other pursubjecting the" same to a high temperature and pressure in a closed receptacle without material distillation, the hydrocarbons being present throughout the treatment in both liquid and vapor phases; transferring material in both liquid and vapor phases to a separate vesseland cooling it therein, the material in the liquid phase being retained during such cooling under pressure of the material in the vapor phase; and finally separating and recovering the desired lighter hydrocarbons from the cooled product.

2. Process of treating liquid or fusible hydrocarbons to produce therefrom hydrocarbons of lower boiling point, jetting the same to a high temperature and pressure in a closed receptacle without material distillation, the vapor space initially exceeding the liquid volume and the hydrocarbons being present throughout the treatment in both liquid and vapor phases; transferring material in both liquid and vapor comprising subphases to a separate vessel and cooling'it In testimony whereof I afiix Iny signature therein, the material in the liquid phase bein presence of two Witnesses.

in retained durin such coolin under pressu i e of the material in the vapoi phase; and PREVOST HUBBARD finally separating and recovering the de- Witnesses: sired lighter hydrocarbons from the cooled C. P. TOWNSEND,

product. C. W. FOWLER. 

